The present invention is directed to a device for use with a conventional grinding machine for sharpening single-flute countersinks, which countersinks are used to form a countersink in a surface receiving a screw, or the like. Countersinks come in many different numbers of flutes, or cutting edges, with the generally more common one being the single flute countersink, which is used for all types of surfaces. Hithertofore, when such a single-flute countersink has been used alot and has become dulled, there has not been any feasible and economical manner by which such single-flute countersink may be re-sharpened for continued use and prolonged life. Usually, these worn countersinks are simply discarded and replaced by a new one. Conventional grinding machines are not capable of sharpening these single-flute countersinks, as they may sharpen conventional drill bits. There are many drill-bit attachments for surface grinding machines, but these can only be used to sharpen and renew drill bits, not countersinks, and especially not single-flute countersinks.